Abstract: In order to reveal the effect of main phenolic substances on the growth of black spot Alternaria alternata after fruit harvesting, and on the basis of the analysis of the content of Pingguoli pear peel phenolic substances during the development and storage period, this paper studied the effects of seven phenolic substances in the Pingguoli pear peel on the spore germination, mycelium growth, mycelium dry weight and melanin formation. The results showed that, in addition to arbutin, phenolic acids and flavonoids had a certain inhibitory effect on the germination of A. alternata, and there was a concentration dependence, and the inhibitory effect was phenolic acids> flavonoids> simple phenols, in turn. The inhibitory effect of ferulic acid was strong, and the spore germination, mycelial growth and dry weight of mycelium treated with 3 mg/mL ferulic acid were reduced by 98.5%, 29.4% and 22.2% respectively compared with the control (0 mg/mL). At the same time, the content of A. alternata melanin was increased in varying degrees after the treatment of seven phenolic substances. It can be seen that phenolic substances in Pingguoli pear peel have an important regulatory effect on the growth and pathogenicity of A. alternata.